Mixer



March 6, 1951 ROCKBURG 2,544,545

MIXER Filed Dec. 11, 1948 INVENTOR. GEORGE. A. ROCKBURG ATTORNEY Patented Mar. 6, 1951 UNITED STATES PATENT OFFICE MIXER George 'A. Rockburg,'Milwaukee, Wis, assignor to "The '1. L. E Smith Company, Milwaukee, "Wis, a

corporation'of .Wisconsin Application December 11, 1948,]SeriaLNo. 64,745

9 claims. 1

This invention relates to concrete mixers of the type having ahopper discharging'into \the endl of a mixing drum .as commonin truckmixers. More particularly, this invention relates'to the arrangement for sealing the-bearing between the hopper and the rotatable annular -.end plate associated with the drum.

Truck mixers generally have arotatable mixing drum mounted on the frame with the open-end or mouth at the rear. IIhedrum is provided with internal mixing elementswhich may'aid charging when the drumrotates in one direction-and aid discharging when rotation is reversed,,0r itmay be rotated in the same direction at all times. The majority oftruck mixers have a charginghopper which is movable intoand. out of contact with the drum mouth While othersvareprovided with a hopper carried'by the drum and mounted ina bearing so the hopper may bemaintained stationary while the drumrotates. In either construction the hopper discharges into thedrum centrally of the mixing elements and.is,.therefore, provided with an annular end plate -.to close the space between the hopper andthe drum. .In the first construction mentionedthe ,closureplate is rotatable on abearing carried by the hopper and seats on i'the'drum. mouth for rotation therewith while the other constructionemploysa plate.integral with the drum and-having'j the hopper ,centrally located therein and mounted in ,aJoear- Thus it willbe apparent that both constructions have. a bearingbetween thehopper and thaend plate. It is obvious'that'fine,particles fromthe mix or grout in-the drum wouldrshortlyrdestroy the bearing, and. to prevent damage a seal is,.generally utilized to revent direct contact of .the mix with the" bearing. 'iVhile any such bearing and seal must belubricated torender proper service, the problem of providinga single sealof high efficacy and long life? has, notbeensatisfactorily solved in the prior art. Indeed, the trend has been toward more complex structures having high initial cost and being expensive anddiflicult to replace when worn.

The principal object of thisv invention .isto ,provide a simple sealing arrangement having high efiicacy and long life.

Another object isto provide a sealingarrangement which compensatesi'for wear without losing its efficacy.

A further object is'to provide asealingarrangement which relieves pressure on the bearing,.thus providing a more 'free running bearing andvadding to bearing life.

Still another object is :to provide a low cost sealing arrangement having high eflicacy andlong life and being readily replaceable.

Other objects and advantages .will be pointed outv in, orbe apparent from, the; sp-ecificationand claims, as .will obvious modifications of the single embodiment-shown in'the drawings,,-in which:

Fig. 1 is a fragmentary side elevation ,of a charging hopper and drum provided with mysealing arrangement and having parts broken away andin section; V jFlg. 2 is a view taken on 1ine-2-.2 of Fighil; and

-Fig. 3 is an enlarged sectional sview of the bearing and sealshown in Fig. .1.

Referring to the drawings in detail, Figs. 1 toBillustrate a charging hopper it] of the type {suspended iromandcarried byrhangers or arms &2 pivoted ion the truck ,frame 14 v for moving .therotatably mounted closure or end; plate I fiiinto and out of contact-- with the drip ring 18 on :the mouth of mixing drum 28 in responsetogmovement imparted to the hangers through link 22 byr lactuation: of hand crank 24 or-;other suitable means. This actuating mechanism does not form apart of:this invention but is;preferab1y-as:shown in any co -pending application Serial No. 58,782. It shouldbe noted,-however, that the force :seatmg the elosure plate on the 1 drum mouth.- is applied totthe non-rotating hopper-:by the hangers through a :laterally projecting stud '26-on each side of-"the hopper.

The frusto-fconical or dishedclosuregplate 16 is rotatably carried on the :hopper by means of a bearing to permit the plate to :.rotate with the drum when sea-ted thereon. (It will-be evident that the end plate could be flat rat-her than dished.) Thus an annular plate v28 -is welded or otherwise secured to :hopper in and a bearing piece 3'6 secured to its outer periphery by bolt 3!. is providedwith an annular notch 32 which is adapted to receive a second bearing piece 34 havingaaecomplementary tongue-36. This construction,, as clearly shown inthe drawings, mounts thee-11d plate 1.6 rotatably on the hopper .assembly while providing for limited relative axial movement between ,the bearing pieces 30 and-34. However, the interfitting tongue and notch constructionprecludes axial separation of thepieces inane-direction, while means to be later described precludes axial'separation of the piecesimthe opposite direction. The bearing piece 341s connected by webs 3B todannular mountingvpiece 31 which is connected to endplateJB by bolts 39.

The outer face of this-bearingpiece This construction provides arcuate openings 40 (Fig. 2) for a purpose to be described hereinafter. Lubricating grease is introduced into the bear ing through grease fitting 42 approximately at the base of notch 32 in the stationary bearing member 39. Leather or neoprene annuli M, 46 may be mounted in the stationary bearing piece to effect a seal tending to retain the grease in the bearing.

As is well known, the bearing between the stationary hopper and the rotating end plate cannot perform satisfactorily unless sealed from the contents of the mixing drum since the fine partioles in the mix shortly destroy bearing surfaces. To obtain a highly eflicacious seal a neoprene or rubber annulus 48 is stretched until its inner periphery may be fitted into notch 50 in the steel sealing ring 52 where it is retained by the natural resiliency of the material. The outer periphery of the elastic ring 48 is then securely mounted in the groove 54 between end plate I6 and mounting piece 31. As shown more clearly in Fig. 3, the inner face of the bearing piece as is provided with an inwardly directed sealing face designed for engagement by the sealing face of the seal ring 52. The inner face of the bearing piece 39 is positioned at a point along the drum axis closer to the drum than the position the seal member would occupy in a normal, unstressed condition of the elastic ring, so that when the parts are engaged as shown in Fig. 3, the inner periphery of the elastic ring 48 is displaced or offset axially towards the drum in respect to the outer periphery of said ring to thereby stress in shear the elastic body of the ring. ihe elasticity of ring 48 naturally urges ring 52 into contact with the inner face of bearing piece 39 and also precludes axial separation of the bearing pieces in a direction opposite to that previously referred to in respect to the interfitting notch and tongue members 36 and 32. This force is greatly enhanced by providing an annular, radially-extending flange 58 on one face of ring 52 terminating close to the inner surface of mounting piece 31 to place the rubber ring 48 in direct shear. This construction additionally serves to tend to move the ring axially in a bodily fashion, thus reducing the tilting action of the sealing ring. However, there may be some tilting action and for this reason the inner face of stationary bearing 30 may be slightly beveled at 68 (exaggerated in Fig. 3) to obtain a fiat seating surface between the sealing ring and the bearing face. Grease is, of course, introduced between these surfaces to provide for freer running and prevent entrance of grout.

Obviously, if grease is not supplied to the seal, grout may work past the seal. If the lubrication is thus neglected, the grout will fall out of arcuate openings 40 and the danger of damage to the bearing is reduced to a minimum. To prevent any such possibilities due to inadequate lubrication, it is preferred that the parts be automatically lubricated as shown in the co-pending Rockburg et a1. application Serial No. 64,572.

The elasticity of the assembly will compensate for wearing of the seal with use, thus maintaining high efiicacy. At first blush it would appear that the rubber in shear tends to force the bearing surfaces together and increase the bearing load. This is the case only when the end plate is not seated on the drum mouth and the bearing parts are not rotating, thus being of no consequence. When the hopper hangers l2 are swung down to move the end plate into contact with the drip ring, the force is applied to the stationary parts. Therefore, after initial contact is obtained between the end plate and drip ring, further movement of hangers l2 drives the stationary bearing piece against the sealing ring, thus increasing the shearing force on the rubber and increasing the sealing force while simultaneously relieving bearing pressure to provide a freer running bearing.

The simplicity of this seal as opposed to prior structures will be readily appreciated. The manufacturing cost is low and maintenance is both simple and inexpensive with the components being readily replaceable. For example, the short leg 59 of the notched end of the sealing ring 52 permits the rubber annulus 48 to be readily removed and replaced. While the embodiment shown illustrates my invention applied to the type of charging hopper which is pivoted on arms carried by the frame so that the end plate may be moved into or out of contact with the drip ring on the drum mouth, it will be apparent that this invention permits of ready application to those structures wherein the charging hopper assembly is carried on a shaft extending along the drum axis and on those structures wherein the end plate is integral with the mixing drum and the hopper is rotatably mounted in the center of the drum-carried end plate where it may be retained in a stationary position with the hopper end up for charging or in a stationary position with the open hopper end facing down for discharging since all of these truck mixer structures embody a stationary charging hopper mounted centrally of the end plate.

Obvious modifications will occur to those skilled in the art. For example, the rubber ring 48 may be replaced by other elastic materials such as spring steel (which would be in the form of arcuate segments), etc. The form of the parts may be changed without departing from the spirit of this invention. For these reasons this invention is to be limited only by the scope of the claims.

I claim:

1. A mixer including a mixing drum rotatable about its axis and having an opening in its end, a charging hopper assembly adapted to discharge into said drum centrally of said opening, an end plate adapted for rotation with said drum, bearing means between said hopper assembly and said end plate to permit relative rotation therebetween, said bearing means comprising first and second bearing pieces, said first piece being mounted on said hopper assembl and having an annular surface facing the drum interior, said second piece being carried by said end plate and cooperating with said first piece to retain said hopper assembly and said end plate in assembled relationship, and sealing means between said end plate and said hopper assembly to prevent mix in the drum from contacting said bearin means, said sealing means including, an. annular elastic ring having its outer periphery mounted in said end plate, an annular seal mounted on the inner periphery of said ring and contacting said annular surface, said outer periphery of said ring and said annular surface being offset with respect to the drum axis to stress the elastic ring in shear and resiliently maintain said seal in contact with said annular surface, said annular surface being tapered with respect to a plane normal to the drum axis to insure an annular seating surface between the seal and the surface when the seal cocks with respect to a plane normal to said axis due to the shear action on said elastic ring.

-2. Amixer including a r'nixing :drum rotatable about its axis. and having an: opening in its end, a charging hopper assembly adapted to discharge intosaid drum.centrally of said opening, an end plate adapted for rotation with said drum, bearingmeans between said hopperassembly-and said end plate to permit'relative rotation .therebetween, saidbearingm'eans comprising first and second bearing pieces, said first piece being mounted on saidhoppenassembl and havingan annular surface facing the drum interior, said secondipiece being carried by said end'plateiand cooperating with said first/"piece to retain said hopper. assembly and said'end plate (in assembled relationship, and sealing: means between said end plate and said hopper assemblytoipreventmix in the drum from contacting said :bearing'means, said sealing means including, an annular elastic ring having itsouter periphery mounted in said endplate, an annular seal'mounted onthe inner periphery of said ringiand contacting'said annular surface, said outer periphery of-saidringand said annular surface beingnifset with respect to thetdrum axis to stressthe elastic ring in shear and resiliently maintain said seal in contact with said annular surface, the outer'peripher iof said seal being in close'proximity to the end plate where the elastic ring is mounted so thatthe shearstress is confinedto a small portionof the elasticring and the tendency of the sealtocock out of normal with respect to the drum axis is minimized, saidannular surface being tapered with respect to a plane normal to the drum axis to insure anannular seating surface between the seal and the surface when the seal cocks with respect to a plane normal to said axis due to the shear action on said elastic ring.

3. Ina concrete mixer, a'rnixing drum having an open end, a charging hopper assembly adapted to discharge mix intothedrum through said opening, an annular end plate, bearing means mounting said end plate on said hopper assembly for relative rotation thereon andproviding relative axial-movementbetween the-'end-plate and the hopper assembly, manually actuated means acting on said hopper assembly for moving said hopper assembly and said end plate axially with respect to said drum from a charging position in which said plate seats on said drum end to a discharging position in whichsaid plate is spaced from said drum end, and means sealing said'bearingmeans from the contents of said drum, said' sealing means including an annular member secured to said end plate and extending transversely of the drum axis into sealing engagement with an inwardly facing sealing surface provided on said hopper assembly for transmitting the seating force from said manually actuated means to said end plate.

4. A mixer including a mixin drum having an opening in its end and being rotatable about its axis, a charging hopper assembly, an end plate, means for mounting the end plate for rotation on and for limited axial movement with respect to the hopper assembly including a first bearing member carried by said hopper assembly and having an annular notch facing rearwardly, a second bearing piece mounted on said end plate and having an annular tongue projecting forwardly into said notch, said interfitting annular notch and tongue precluding axial separation of the bearing pieces in one direction, an elastic ring having its outer periphery mounted in said plate, a seal mounted on the inner periphery of said ring and contacting an inwardly facing sealing surface provided on the interior of said hopper assembly, said inner periphery :of said .i'ing .ibeing' displaced axially towards the drum with respect to the outer periphery thereof .to stress said elastic ringin shear, said stressed ring being operative to bias the seal into contactwith the sealing surface of the hopper assembly and to preclude axial separation of said bearingpieces in the opposite-direction, actuatable means carrying the hopper assembly and being operative to move the hopper carried 'enclplate intoand out of .contact with the drum end, application of force on said hopper assembly by saidactuatable means after-the end plate'has contacted the drum end being-opera'tive to increase the bias on 'theseal and decrease the bearing pressure.

- 5. mixer including a mixing drum -mounted 'for rotationabout its axis and having an opening in one end, acharginghopper assembly anend plate adapted to-rotate with the mixing drum, bearing-means for mounting the end plate-on: said hopper assembly for rotation and for relative axial movement with respect thereto and including a'first bearing piececarriedby said hopper assembly and provided'witha' rearwardlyopening annular nctch,-a second bearing piece having an annular forwardly facing tongue projecting-into said notch, Sa-icl interfitting notch and tongue precluding-axial separation'of the bearing pieces in one direction, mountingmea'ns for supporting said second bearing piece on=said-' end plate and having an annular series of arcuate openings therein positioned radiallyoutwardly of saidanniilar tongue, an elastic ring'having its outer periphery: mounted in said plate, a'seal mounted on the inner periphery of saidr-i-ngand contacting an inwardlyfaci-ng sealing surface providedon said hopper assembly, the inner periphery of said elastic ring being ofiset axially towards the drum wlth'respect to the outer periphery ofth-e ring to stress the body of the ring in shear and blast-he seal into contact withthe sealing surface of said hopper assembly, the bias of said elastic ring being operative to resiliently retain said bearing pieces in assembled relationship against 'axial separation in-the opposite direction while maintaining a sealing relationshipbetweensaid-seal and said'hopper assembly-said arcu-atebpenings discharging outwardly any material'leaking past said seal. 7

6. A-mixer including a'mixing'drum rotatable about its axis and having an opening inits end, a "charging hopper "assembly adapted to discharge into said drum centrally of saidopening, an end plate adapted for rotation with said drum, bearing means mounting said end plate on said hopper assembly for relative rotation thereon and providing relative axial movement between the hopper assembly and said end plate, said bearing means comprising first and second bearing pieces, said first piece being mounted on said hopper assembly and having an annular sealing surface facing the drum interior, said second piece being carried by said end plate, said bearing pieces including transversely disposed radially overlapping parts cooperating to preclude axial separation of said hopper assembly and said end plate in one direction, and sealing means between said end plate and said hopper assembly to prevent mix in the drum from contacting said bearing means, said sealing means including an annular elastic ring having its outer periphery mounted in said end plate, an annular seal mounted on the inner periphery of said ring and contacting said annular sealing surface, said outer periphery of said ring and said annular sealing urface being offset axially with respect to the drum axis to stress the elastic ring in shear to resiliently maintain said seal in contact with said annular sealing surface to preclude axial separation of aid hopper assembly and end plate in the opposite direction, said annular seal being provided with an annular radial flange overlying said elastic ring on the face thereof remote from the drum, the outer periphery of said flange terminating in close proximity to the end plate where the elastic ring is mounted so that the shear stress in the ring is confined to a relatively narrow annular portion of the elastic ring and the tendency of the ring to cock out of normal with respect to the drum axis is minimized.

7. A mixer including a rotatable mixing drum having an open end, a charging hopper assembly including an annular end plate, bearing means mounting the end plate on the hopper assembly for rotation with respect thereto and providing relative axial movement between the end plate and the hopper assembly, said hopper assembly being carried on actuatable means for moving the hopper assembly carried end plate into and out of contact with the open drum end and for exerting a seating force on the hopper assembly, an elastic ring having its outer periphery mounted on said plate, an annular seal mounted on the inner periphery of said ring and contacting an inwardly facing sealing surface provided on said hopper assembly, said inner and outer peripheries of said ring being displaced with respect to the drum axis to stress said ring in shear and bias said seal into contact with said surface, an increase in said seating force exerted on said hop- 1 per assembly by said actuatable means when seating said plate on said drum end being operable to increase the stress in said elastic ring.

8. A mixer including a drum, an annular end plate rotatable with said drum, a hopper assembly for discharging mix into the drum centrally of said annular end plate, bearing means mounting said end plate on said hopper assembly for relative rotation therebetween and providing relative axial movement of the end plate and hopper assembly, said bearing means including means precluding axial separation of the end plate and hopper assembly in one direction, an annular elastic ring having its outer periphery mounted in said end plate, an annular seal mounted on the inner periphery of said ring and contacting an inwardly facing sealing surface provided on said assembly, said inwardly facing sealing surface being axially offset towards the drum with respect to the axial position of said seal member in the normal, unstressed condition of said elastic ring to stress said elastic ring in shear when the annular seal and said inwardly facing sealing surface are operatively engaged to thus bias the seal into contact with said sealing surface and to preclude axial separation of the hopper assembly and end plate in the opposite direction.

9. In a concrete mixer, a mixing drum having an open end, a charging hopper assembly adapted to discharge mix into the drum through said opening, an annular end plate, bearing means mounting said end plate on said hopper assembly for relative rotation therebetween and providing relative axial movement between the end plate and hopper assembly, manually actuated means acting on said hopper assembly for moving said hopper assembly and said plate axially with respect to said drum from a charging position in which said plate seats on said drum end to a discharging position in which said plate is remote from said drum end, and means sealing said bearing means from the contents of said drum,

, said bearing means including annular portions extending transversely of the axis of rotation of the drum and overlapping radially to preclude axial separation of the bearing members in one direction, said sealing means including an annular member secured to said end plate and extending transversely to the drum axis into engagement with an inwardly facing sealing surface provided on said hopper assembly for holding said bearing means in assembled relationship and precluding axial separation of the end plate and hopper assembly in the opposite direc- GEORGE A. ROCKBURG.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,167,669 Molyneux Aug. 1, 1939 2,265,751 Ball Dec. 9, 1941 2,265,752 Ball Dec. 9, 1941 2,289,274 Krug July 7, 1942 2,360,345 Hilkemeier Oct. 17, 1944 2,374,912 Barnes May 1, 1945 2,454,940 Peters Nov. 30, 1948 

